#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include<sys/types.h>
#include<unistd.h>
// void handler(int sig)
// {
//  pid_t id;
//  while( (id = waitpid(-1, NULL, WNOHANG)) > 0){
//  printf("wait child success: %d\n", id);
//  }
//  printf("child is quit! %d\n", getpid());
// }
int main()
{
 signal(SIGCHLD,SIG_IGN);
 pid_t cid;
 if((cid = fork()) == 0){//child
 printf("child : %d\n", getpid());
 sleep(3);
 exit(1);
 }
 while(1){
 printf("father proc is doing some thing!\n");
 sleep(1);
 }
 waitpid(-1, NULL, WNOHANG);
 return 0;
}